Cycling is a very popular activity for both recreational riders and racing enthusiasts alike. Professional cyclists and triathletes are earning large sums of money through races, sponsorships, and advertisements. Moreover, cycling provides many health benefits for average riders in that it strengthens various muscle groups along with providing aerobic and anaerobic exercise to the user. Furthermore, physicians and physical therapists are turning to stationary cycle devices to rehabilitate patients from automobile, athletic, or work-related injuries. Because of this, there is a demand for indoor, stationary trainers that simulate actual outdoor riding so that professional and recreational cyclists may train or exercise regardless of the weather, and that patients can rehabilitate injuries in the presence of their physicians and physical therapists.
Various stationary cycle trainers have been presented to address this need. Conventional stationary cycle trainers simulate the characteristics of outdoor training by applying a variable resistance device to provide resistance against the pedaling of the rider. The variable resistance device mimics the resistances a rider would face during actual outdoor training such as wind resistance, rolling resistance, and resistances due to riding over varying terrain. Recently, the use of “eddy current” trainers have achieved widespread use due to their ability to simulate the resistance (loads) felt by riders during actual riding.
In one prior art “eddy current” trainer shown in FIG. 1, the trainer 10 includes an eddy current brake 12 that is coupled to the rear wheel 14 of a bicycle 16. The eddy current brake 12 includes a shaft 18 that is placed in rotational contact with the rear wheel 14 of the bicycle 16. As the rear wheel of the bicycle rotates, it rotationally drives the shaft.
The eddy current brake 12 further includes a conductive disk (not shown) that is coupled to the shaft 18 and is disposed between a plurality of electromagnets (not shown). When the rider rotates the pedals of the bicycle, the conductive disk rotates via the shaft 18 and the rear wheel 14. As the disk rotates, the electromagnet's magnetic fields induce eddy currents within the rotating disk. The eddy currents in turn produce electromagnetic fields that interact with the electromagnet's magnetic fields. This interaction of electromagnetic fields produces a resistance to the rotation of the disk, and thus the shaft 18 and rear wheel 14 of the bicycle 16.
The use of electromagnets allows individual or groups of magnets to be energized at specific times and voltages to produce variable torques, and resistances to the rotation of the bicycle's rear wheel. The use of electromagnets allows the resistance or braking force to be set to any desired level, or varied in order to duplicate actual road conditions experienced by the bicycle rider. Trainers incorporating such an eddy current brakes can take into account wind resistance, head winds, changes in elevation, rider inertia, rolling resistance, the effects of drafting, etc.
Further advancements in “eddy current” trainers allow for the monitoring and evaluation of the rider's or patient's performance during the exercise session. These trainers use a microprocessor/sensor arrangement to calculate several session perimeters such as heart rate, energy exertion, time elapsed, and distance. The microprocessor is also connected to an electric drive circuit that energizes the electromagnets at predetermined times and power levels in order to simulate changes in terrain. An eddy current trainer that uses electromagnets to simulate real life bicycling road conditions, and that uses a microprocessor to evaluate the user's performance, is sold under the trademark COMPUTRAINER by Racermate, Inc., Seattle, Wash.
Although the use of electromagnets and microprocessor has dramatically improved the “eddy current” trainers, there are still limitations that exist. For example, the arrangement of the rear wheel contacting the shaft of the resistance brake requires the user to exert a minimum power output of around 50 watts to just get the rear wheel and the conductive disk to rotate. Some rehabilitation patients cannot exert this amount of power. Additionally, the contact of the rear wheel against the shaft does not allow the user to coast. Furthermore, the friction losses due to the prior art arrangement only allows the measurement of the exercise session perimeters to be accurate within 1–2%.